For example, PTLs 1 and 2 describe known cutting inserts that are used for milling cutters.
The cutting inserts disclosed in these PTLs are of a so-called vertical-use type that uses a rectangular surface, which is usually called a side surface, as a rake face. By using the vertical-use type cutting inserts, high-feed high-efficiency machining can be performed because the cutting inserts each have a large thickness and a high rigidity in a direction in which the cutting insert receives a main component of a cutting force.
The cutting insert of PTL 2 has minor cutting edges that are formed by cutting out corners of a rectangular side surface, which serves as a rake face. A minor cutting edge is formed at each of the corners so that the minor cutting edge intersects a major cutting edge, which is a long side of the side surface, at an angle of approximately 45°. Thus, by attaching the cutting insert to a cutter body so that the major cutting edge forms an approach angle of 45°, the minor cutting edge is made to function as a flat cutting edge.